Multi-circuit safing and arming switch

ABSTRACT

An inertia responsive, non-latching, multi-pole, normally open, single throw switch, whose pole piece while in a &#39;&#39;&#39;&#39;safe&#39;&#39;&#39;&#39; position will not unlock nor close the switch contacts until the switch has experienced the three sequentially applied environmental accelerations, such as found in a projectile when it has been launched from a weapon. The present device comprises an inner end cap pole locking means, a hollow cylindrical insulator axially aligned with the locking means and proximately fixed thereto, a terminal support means affixed to the other end of the cylindrical insulator, a plurality of lead spring contacts peripherally disposed within the support means and exiting therefrom as electric switch contact leads, a flexible axially positioned cantilever operatively positioned in the support means, a biasing means for holding a slidable interlocking pole means on the cantilever and maintaining the switch in an open safe position until two of the three sequential accelerations found in a gun barrel cause the pole means mass to bend the cantilever away from the locking means, releasing the pole means therefrom, thereby permitting the centrifugal force of spin to overcome the biasing means and sliding the pole means toward the switch contacts and closing the switch so that the projectile is armed.

United States Patent [191 Buxton Nov. 13, 1973 MULTI-CIRCUIT SAFING AND ARMING SWITCH [75] Inventor:

Ralph Buxton, Arnold, Md.

The United States of America as represented by the Secretary of the Army, Washington, DC.

Nov. 13, 1972 Assignee:

Filed:

Appl. No.:

U.S. Cl 102/70.2 R, 102/80, 200/61.45 R Int. Cl. F42c 15/40, F42c 11/00 Field of Search l02/70.2 R, 80;

ZOO/61.45 R

9/1968 Webb 102/80 4/1973 Wagnecz l02/70.2 R.

Primary ExaminerSamuel Feinberg Assistant Examiner-C. T. Jordan Attorney-Harry M. Saragovitz et al.

[57] ABSTRACT An inertia responsive, non-latching, multi-pole, normally open, single throw switch, whose pole piece whilein a safe" position will not unlock nor close the switch contacts until the switch has experienced the three sequentially applied environmental accelerations, such as found in a projectile when it has been launched from a weapon. The present device comprises an inner end cap pole locking means, a hollow cylindrical insulator axially aligned with the locking means and proximately fixed thereto, a terminal support means affixed to the other end of the cylindrical insulator, a plurality of lead spring contacts peripherally disposed within the support means and exiting therefrom as electric switch contact leads, a flexible axially positioned cantilever operatively positioned in the support means, a biasing means for holding a slidable interlocking pole means on the cantilever and maintaining the switch in an open safe position until two of the three sequential accelerations found in a gun barrel cause the pole means mass to bend the cantilever away from the locking means, releasing the pole means therefrom, thereby permitting the centrifugal force of spin to overcome the biasing means and sliding the pole means toward the switch contacts and closing the switch so that the projectile is armed.

5 Claims, 4 Drawing lFigures 92 z 92 3 4 7a .54 5 .94 861 98 4 44 r 4 56 i q I 56 I00 46 34 76 6 0 f /0 M 1 /4 A a \26 5 la l 2287 2430 L /6 L PATENTED NOV 13 I973 V M m SHEET 1 [1F 3 MULTI-CIRCUIT SAFING AND ARMING SWITCH GOVERNMENTAL INTEREST The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION Various means have been used in the prior art to safe and arm artillery projectiles in order to prevent malfunctions and premature detonation of the projectile warhead when it is still in the gun or near the launch crew. These prior art devices have used both setback and spin forces to mechanically enable or unlock a control mechanism that was essential for the initiation of a detonation. The problem of accidental detonation and non-arming after the projectile has been fired has existed since the development of artillery projectiles. Although many of the prior art devices have utilized the two projectile environments of set back and spin to safe and arm, however, none have utilized the available three environmental forces present in all spin stabilized projectiles namely, centrifugal, angular, and longitudinal acceleration. As a consequence prior art devices are not as safe as the present invention for the former need only two environments, setback and spin, while the present invention utilizes in addition angular acceleration. The probability of a projectile warhead, having the present safe and arming device therein, being accidentally subjected to the three arming environments found in a gun barrel and not being propelled therefrom is extremely low.

The present invention is superior to prior art devices insofar as it requires a combined setback force and angular accelerating force to merely change the device from the safe position to an armed position, and then a subsequent centrifugal force of a specific magnitude to effect switch closure. The present invention is also preferable over prior art inertial switch devices in that it can simultaneously complete a plurality of independent electrical circuits. In addition the present device because of its relatively small size can be used advantageously in applications having severe space limitations. For example, the present device may be made cylindrical in shape having a diameter of approximately three-tenths of an inch and a length from one-half to three-fourths of an inch depending on the number of circuits desired. The present device, as an electrical arming switch, is reliable because it is of rugged construction and has a minimum number of moving parts. The present device also has the desirable characteristic of low contact resistance. Inherent in the operation of the device is the wiping action of a slidable pole means across terminal contact surfaces, this motion tends to remove oxidized layers between surfaces. Unlike some prior art safe and arm devices for artillery projectiles the present invention is not dependent upon spin rate of the projectile for maintaining contact pressure between the pole means and the switch contact in order to maintain low contact resistance.

The present invention insures a reliable inertial switch having a plurality of electrical contacts which can be used for both safing and arming a spin stabilized projectile.

SUMMARY OF THE INVENTION The present invention relates to an electric, safing and arming, normally open, multi-pole, single throw switch whose slidable pole piece, supported by a flexible cantilever member, becomes unlocked when the switch is subjected sequentially first to a combined set.- back force due to linear acceleration coupled with a rotational force due to angular acceleration, followed secondly by a centrifugal force which causes linear motion of the pole means and closure of the switch. The cylindrically configured switch is mounted so that its longitudinal axis is normal to the missiles longitudinal axis and its inner cap end, which locks the pole means, is directed toward the projectiles axis.

The unlocking sensitivity of the present device to the inertial forces of setback and angular acceleration can be readily varied by changing the density and shape of the sliding pendulous mass pole means, and the length, diameter, form, and material of the supporting cantilever. The sensitivity of the device to effect switch closure as a result of the centrifugal forces can be readily varied by changing the compressive force exerted by a spring biasing means on the pole means. The present device resafes itself in the event there is a faulty firing which fails to give the projectile enough spin. When the spin rate falls below a minimum level the spring biasing means forces the sliding pendulous mass clear of the contacts thereby reopening the switch and permitting the slidable pole piece to relatch itself and resafe the projectile. This resafing feature is of particular importance when a firing fails to develop a sustained spin environment which may cause the projectile to fall short of its intended range, thus preventing possibly injury to friendly personnel.

One of the objects of this invention is to provide a multi-circuit safing and arming switch which is sequentially responsive only to three acceleration environments such as found in artillery gun barrels.

Another object of this invention is to provide a multicircuit safing and arming switch which is responsive to three acceleration environments and is non-latching.

Another object of this invention is to provide a multicircuit safing and arming switch which will resafe itself when the projectile to .which it is operatively affixed fails to attain a minimum level of spin.

Another object of this invention is to provide a multicircuit safing and arming, acceleration responsive switch which lends itself to miniaturization and is adaptible for incorporation into projectiles having small system volume.

Another object of this invention is to provide a multicircuit, safing and arming, acceleration responsive switch which will maintain a stabile closed position as long as minimum projectile spin is maintained.

Another object of this invention is to provide a multicircuit, safing and arming, acceleration responsive device which has a minimum of moving parts and whose operation is simple and therefore mechanically reliable.

Another object of this invention is to provide a multicircuit safing and arming, acceleration responsive switch which has low contact resistance.

Another object of this invention is to provide a multicircuit safing and arming, acceleration responsive switch whose contact pressure and contact resistance is independent of spin rate.

A further object of this invention is to provide a multi-circuit safing and arming, acceleration responsive switch which can be sealed with an inert gas to resist contact oxidation and increasing contact resistance as BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of the multi-circuit safing and arming switch in the safe position taken along a radial plane through its longitudinal axis.

FIG. 2 is a cross-sectional view of FIG. 1 taken in the direction of line 22 in order to show the constructional details of the inner end cap restraining ledge and the annular locking groove of the sliding pendulous mass.

FIG. 3 is a cross-sectional view of FIG. 1 taken in the direction of line 33 showing the positions of leaf spring contacts relative to the switch body, outer end cap, cantilever support beam, sliding mass and biased helical spring.

FIG. 4 is a cross-sectional view of FIG. 1 taken in the direction of line 4-4.

Throughout the following description like reference numerals are used to denote like parts of the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, the cylindrically shaped multi-circuit safing and arming switch has a longitudinal axis 10. An axially aligned tubular body 12 is composed of an insulating material, such as LEXAN, an inner body end 14, an outer body end 16, an axial bore 18 disposed adjacent to the inner end 14, an axial counterbore 20 disposed adjacent to the outer end 16, and an intermediate tapered bore 22 having its larger end adjacent to the axial bore 18 and its smaller end adjacent to the counter bore shoulder 24. A slotted cup shaped outer end cap insulator 26 fitting into counterbore 20 closes outer body end 16 with its hermetically sealed lead end 28 and its slotted open end 30 abuts against counter bore shoulder 24. Outer end cap 26 has a central axial bore 32 for fixedlyholding an axially aligned tubular cantilever support member 34 therein. The tubular support member 34 has an axial beam bore 36 on one end which fixedly holds therein a flexible canti-lever beam 38 on the beams fixed end 40. A tapered axial counterbore 42 has its smaller end 44 disposed adjacent to beam bore 36 and forms a holding well for the rear spring end 48 of the compression biased helical spring 46. The front spring end 50 biasedly pushes the sliding pole means mass 52 toward the restraining ledge 54 of the inner end cap insulator 56. The sliding pole means 78 is held in this forward position until such time as the three environmental accelerations are imposed upon the switch by the weapon. The combination of setback and angular acceleration causes bending of cantilever 38 and freeing of the tapered front end 80, thereby permitting it to move in a direction which releases it from the restraining ledge 54 and the short inner end cap wall 55 and permitting the centrifugal force to move the pole means 78 toward the outer end cap 26. A stop 58 fixedly attached to the free end 60 of cantilever 38 prevents the sliding pole mass 52 from sliding off the free end 60 thereby maintaining the bias of spring 46. A compliant foam rubber tubular spring support 62 is held intermediate the helical spring 46 and the cantilever beam 38 preventing bowing and subsequent binding of the spring 46 during setback. A plurality of pairs of normally open leaf spring contacts 64 and 64 as shown in FIG. 1, and 64 64, 66 66', 68 68 and 70 70' as shown in FIG. 3 are peripherally spaced around and longitudinally staggered along the circumferance of insulator 26. The leaf springs aforementioned have their front free contact ends 72 peripherally positioned in the slotted open end 30 of the outer end cap 26. The leaf spring contact fixed sections 74 are held intermediate the axial counterbore 20 and the outer end cap 26, and protrude rearwardly therefrom as electric contact leads 76 for the switch. The cylindrically shaped sliding pole means assembly 52 consists of a front locking section 78, a'rear holding section 90, a plurality of gold plated shorting rings 92 and a plurality of insulating space rings 94. The sliding pole means 78 has an axially aligned tapered front end 80, a longitudinal axial locking section bore 82, a concentric friction reducing bore 83 of slightly larger diameter, a necked down cylindrical section 85 intermediate to a front washer holding shoulder 84 and the tapered front end 80, and an integral externally threaded cylindrical rear end spindle 86 having its longitudinal axis concentric with the tapered front end 80. An annular locking groove 88 is transverse to the longitudinal axis 10 and intermediate front end 80 and holding shoulder 84. Therear holding section 90 threadedly affixed to the threaded washer spindle 86 by the internally threaded bore threads 96 has a complementary rear holding shoulder 98, a rear holding section axial bore 100, and a spring positioning boss 102 for holding the front spring end 50. Positioned intermediate the front and rear shoulders 84 and 98 are alternately positioned shoring rings 92 and insulating rings 94. Generally a relatively inert gas 106, such as a neon, nitrogen or argon, may be put into the residual switch volume to help reduce oxidation and to maintain near constant contact resistance. A preferable embodiment of this invention utilizes a silicone grease in the switch volum'e instead of the inert gas 106 to act as a dampening agent and to help prevent damage to the structural parts caused b vibrations due to high velocity motion.

FIG. 2, a cross section taken in the direction of line 22, shows how the tapered front end 80 is restrained by ledge 54 in the upper right hand quadrant and in the lower right hand quadrant by the body 12. The restraining ledge 54 partially encircles the necked-down annular groove 88 when the switch is in a safe" open position as shown.

FIG. 3 shows the constructional detail of a plurality of diametrically paired peripherally spaced and longitudinally staggered leaf spring contact 64 64', 66 66, 68 68 and 70 70' respectively, electrically insulated and physically separated from-each other by the radially slotted longitudinal outer end cap ribs 104.

FIG. 4, a cross section of FIG. 1 in the direction of line 44, shows how the peripherally located pairs of electric contact leads 64 64', 66 66', 68 68' and 70 70' pass into and through the outer end cap 26.

In operation the multi-circuit safing and arming switch is positioned in a projectile (not shown) so that the switchs longitudinal axis is normal to the longitudinal axis of the projectile with the inner end cap 56 pointing toward the projectile axis. During launch of the projectile the device is subjected to three distinct acceleration environments. The setback inertial force, acting along the shell axis, combined with the angular acceleration inertial force due to projectile spin, causes the cantilever sliding pendulous pole means to bend the beam 38 in a direction radially away from the restraining ledge 54. The centrifugal force acting on the mass 52 along the projectile radius and the switch longitudinal axis overcomes the compression coil spring 46 causing the sliding mass gold plated shorting rings 92 to touch the paired peripherally spaced leaf spring 72 thereby closing the circuit. The helical spring 46 is selected so that the sliding pole means 52 will bottom against the outer end cap 26 only at an established minimum spin speed. This spin speed is based on the minimum decayed spin rate of the projectile in its lowest and coldest firing zone. If the spin rate falls below this minimum level or the projectile falls short of the target, the helical spring 46 will force the sliding pole means mass 52 clear of the metal shorting rings 92. The tapered front end 80 on the sliding mass 52 will now wedge itself under the restraining ledge 54 and deflect the free cantilever beam end 60. Additional force by the biased helical spring 46 against the rear holding shoulder 98, because of insufficient spin, will cause the sliding mass 52 to continue to move toward the stop 58 and to its original prefiring safe position.

I wish to be understood that I do not desire to be lim ited to the exact detail of construction shown and described for obvious modifications will occur to a person skilled in the art.

What is claimed is:

1. A multi-circuit, normally open, single throw electrical switch for safing and arming a projectile in a weapon which comprises:

inner end cap hole locking means;

a hollow cylindrical insulator axially aligned with said locking means having a first open end proximately fixed thereto, a second open end having an axial counterbore therein;

terminal support means axially aligned and affixed to said cylindrical insulator second open end;

a plurality of paired leaf spring contacts peripherally disposed within said support means having front cantilever free contact ends operatively positioned in said support means, electric contact leads rearwardly exiting from said support means;

a flexible axially positioned cantilever having its fixed end operatively positioned in said support means and its free end held within said locking 'means and said cylindrical insulator;

a stop fixedly attached to said cantilever free end;

biasing means circumambient said cantilever and adjacent said support means; and

interlocking pole means slidably positioned on said cantilever intermediate said stop and said biasing means, whereby said pole means bends said cantilever away from said locking means and releases said pole means therefrom when said projectile is subjected to the combined forces of setback and angular acceleration, said pole means under the influence of subsequently applied centrifugal force of spin overcomes said biasing means and moves said pole means in a direction parallel to said cantilever longitudinal axis so that said paired spring contacts are shorted by said pole means, and whereby said pole means mass is forced by said biasing means to return to said locking means resafing said projectile when said projectile fails to attain a minimum level of spin rate.

2. A multi-circuit switch as recited in claim 1 wherein the pole locking means comprises:

a cup shaped cap having a closed end, a partially closed open end having a restraining ledge integrally attached thereto for locking said pole means so that said leaf spring contact pairs are in an open safe position when said projectile is within said weapon.

3. A multi-circuit switch as recited in claim 2 wherein the terminal support means comprises:

a cylindrical outer end cap having a cup shaped closed end, an open end, a partially slotted wall for positioning therein said leaf spring contacts, and a central axial bore intermediate said closed and open ends.

4. A multi-circuit switch as recited in claim 3 wherein the biasing means comprises:

a cylindrical cantilever support member fixedly held within said central axial bore having an axial beam bore on one end adjacent to said support sealed lead end, a tapered counterbore on the other end;

a helical spring biasedly positioned intermediate said pole means and said cantilever support member; and

a tubular compliant spring support intermediate said flexible cantilever and said helical spring for preventing bowing and binding of said helical spring during switch closure.

5. A multi-circuit switch as recited in claim 4 wherein the interlocking pole means comprises:

a locking section having a tapered front end with an axial bore therethrough, a front washer holding shoulder connected to said front end by an intermediate necked down cylindrical section, an integral externally threaded cylindrical rear end spindle concentric with the front end having a friction reducing bore which is concentric and connects with said axial bore;

a rear holding section having a front internally threaded cylinder, a rear axially positioned spring positioning boss, a complementary integral rear washer holding shoulder intermediate said internally threaded cylinder and said boss, and a rear holding section axial bore within said boss;

a plurality of gold plated metal switch contact shorting rings peripherally positioned on said front internally threaded cylinder; and

a plurality of insulator spacer rings operatively positioned on said front internally threaded cylinder intermediate said gold plated shorting rings for electrically isolating said contact shorting rings. 

1. A multi-circuit, normally open, single throw electrical switch for safing and arming a projectile in a weapon which comprises: inner end cap hole locking means; a hollow cylindrical insulator axially aligned with said locking means having a first open end proximately fixed thereto, a second open end having an axial counterbore therein; terminal support means axially aligned and affixed to said cylindrical insulator second open end; a plurality of paired leaf spring contacts peripherally disposed within said support means having front cantilever free contact ends operatively positioned in said support means, electric contact leads rearwardly exiting from said support means; a flexible axially positioned cantilever having its fixed end operatively positioned in said support means and its free end held within said locking means and said cylindrical insulator; a stop fixedly attached to said cantilever free end; biasing means circumambient said cantilever and adjacent said support means; and interlocking pole means slidably positioned on said cantilever intermediate said stop and said biasing means, whereby said pole means bends said cantilever away from said locking means and releases said pole means therefrom when said projectile is subjected to the combined forces of setback and angular acceleration, said pole means under the influence of subsequently applied centrifugal force of spin overcomes said biasing means and moves said pole means in a direction parallel to said cantilever longitudinal axis so that said paired spring contacts are shorted by said pole means, and whereby said pole means mass is forced by said biasing means to return to said locking means resafing said projectile when said projectile fails to attain a minimum level of spin rate.
 2. A multi-circuit switch as recited in claim 1 wherein the pole locking means comprises: a cup shaped cap having a closed end, a partially closed open end having a restraining ledge integrally attached thereto for locking said pole means so that said leaf spring contact pairs are in an open safe position when said projectile is within said weapon.
 3. A multi-circuit switch as recited in claim 2 wherein the terminal support means comprises: a cylindrical outer end cap having a cup shaped closed end, an open end, a partially slotted wall for positioning therein said leaf spring contacts, and a central axial bore intermediate said closed and open ends.
 4. A multi-circuit switch as recited in claim 3 wherein the biasing means comprises: a cylindrical cantilever support member fixedly held within said central axial bore having an axial beam bore on one end adjacent to said support sealed lead end, a tapered counterbore on the other end; a helical spring biasedly positioned intermediate said pole means and said cantilever support member; and a tubular compliant spring support intermediate said flexible cantilever and said helical spring for preventing bowing and binding of said helical spring during switch closure.
 5. A multi-circuit switch as recited in claim 4 wherein the interlocking pole means comprises: a locking section having a tapered front end with an axial bore therethrough, a front washer holding shoulder connected to said front end by an intermediate necked down cylindrical section, an integral externally threaded cylindrical rear end spindle concentric with the front end having a friction reducing bore which is concentric and connects with said axial bore; a rear holding section having a front internally threaded cylinder, a rear axially positioned spring positioning boss, a complementary integral rear washer holding shoulder intermediate said internally threaded cylinder and said boss, and a rear holding section axial bore within said boss; a plurality of gold plated metal switch contact shorting rings peripherally positioned on said front internally threaded cylinder; and a plurality of insulator spacer rings operatively positioned on said front internally threaded cylinder intermediate said gold plated shorting rings for electrically isolating said contact shorting rings. 